Aluminium-oxide wires for superconducting high kinetic inductance circuits

Journal article (2017)

Authors

H. Rotzinger Karlsruhe Institut für Technologie
S. T. Skacel Karlsruhe Institut für Technologie
M. Pfirrmann Karlsruhe Institut für Technologie
J. N. Voss Karlsruhe Institut für Technologie
J. Münzberg Karlsruhe Institut für Technologie
S. Probst Karlsruhe Institut für Technologie
P. Bushev Karlsruhe Institut für Technologie
M. P. Weides Karlsruhe Institut für Technologie
A. V. Ustinov National University of Science and Technology MISiS, Karlsruhe Institut für Technologie
J.E. Mooij Karlsruhe Institut für Technologie, Kavli institute of nanoscience Delft, QRD/Kouwenhoven Lab - QuTech Advanced Research Centre
Research Group
QRD/Kouwenhoven Lab (QuTech Advanced Research Centre) (TU Delft)
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Published Date

01-02-2017

Language

English

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Faculty

QuTech Advanced Research Centre

Department

Qubit Research Division

Research Group

QRD/Kouwenhoven Lab

Abstract

We investigate thin films of conducting aluminium-oxide, also known as granular aluminium, as a material for superconducting high quality, high kinetic inductance circuits. The films are deposited by an optimised reactive DC magnetron sputter process and characterised using microwave measurement techniques at milli-Kelvin temperatures. We show that, by precise control of the reactive sputter conditions, a high room temperature sheet resistance and therefore high kinetic inductance at low temperatures can be obtained. For a coplanar waveguide resonator with 1.5 kΩ sheet resistance and a kinetic inductance fraction close to unity, we measure a quality factor in the order of 700 000 at 20 mK. Furthermore, we observe a sheet resistance reduction by gentle heat treatment in air. This behaviour is exploited to study the kinetic inductance change using the microwave response of a coplanar wave guide resonator. We find the correlation between the kinetic inductance and the sheet resistance to be in good agreement with theoretical expectations.